The overall objective of this proposal is to analyze details of the neurochemicals involved in the processing of information in central respiratory neurons. We propose experiments which are expected to provide answers to questions concerning the chemical neuroanatomy of distinct neuronal elements in regions of the central nervous system associated with respiratory activity. The planned experiments will utilize basic electron microscopic, immunocytochemical, neuroanatomical, as well as electrophysiological methods to address questions relating to the neurochemical organization of pre- and post-synaptic elements involved in central respiratory control. Quantitative electron microscopic analysis will be used to evaluate the functional effect of neurochemically distinct presynaptic elements (bouton terminals) synapsing on respiratory interneurons and motor neurons. Since traditionally, immunocytochemical mapping studies have been conducted in the rat, relatively little data is currently available regarding light and ultrastructural details of immunocytochemically distinct elements in the respiratory nuclei of the cat. In the proposed project, we plan to direct our attention specifically to the cat in order to relate immunocytochemistry, neuroanatomy, and ultrastructure with respiratory physiology. The application of two different neuroanatomical labels, tritium labeled horseradish peroxidase and cholera toxin conjugated with horseradish peroxidase, in combination with immunocytochemistry will enable us to simultaneously visualize structures of known connectivity and neurochemical identity at the ultrastructural level. These studies are aimed at uncovering the neurochemical identity of respiratory interneurons in the medulla oblongata and respiratory motor neurons in the spinal cord. Studies proposed in this project are unique since the neurochemical organization of functionally identified units involved in respiratory control will be examined at the ultrastructural level. In addition, the use of multiple labels will enhance our understanding of the neurochemical and morphological basis for integrative processes underlying respiratory control.